For cutting and grinding, mineral oils, animal and vegetable oils or synthetic oils are frequently blended with a compound having surface-active properties to provide a water-soluble oil agent, and diluted with water so as to be used as a so-called O/W emulsion or the like.
Representative examples of the compound having surface-active properties are fatty acid amine salts, polyoxyalkylene glycols and mono- or di-ether compounds thereof. For instance, in order to increase the antifoaming capabilities and decay resistance of a water-soluble oil agent to a desired level, it has been suggested to blend an amine salt of a ricinoleic acid polymer (see Patent Literature 1). Typically, paraffin chloride has been blended to enhance efficiency in cutting or grinding. However, since it was pointed out that the use of paraffin chloride may lead to emission of dioxin, which is harmful to human body, or the like, it has been suggested to blend a compound such as sulfur or phosphorus in place of paraffin chloride (see Patent Literature 2).